Dynamic magnonic crystal based on a layered ferrite–ferroelectric structure

A dynamic magnonic crystal based on a planar multiferroid ferrite–ferroelectric structure is suggested and studied. A space-periodic electric field applied to the ferroelectric layer converts a regular multi-ferroid waveguide to a periodic structure. An electrodynamic model of a dynamic magnonic crystal is constructed, and its dispersion and transfer characteristics are studied.     

N-alkylation of <Emphasis Type="Italic">N</Emphasis>-trimethylsilylimidazole

The reaction of N-trimethylsilylimidazole with alkyl chloroacetates is studied. This process yields a mixture of N-alkylation and quarternization products in the ratio dependent on the reaction conditions. The reaction mechanism is discussed. ¹H NMR data show that high melting point and low solubility of 1-imidazolylacetic acid in organic solvents are evidently caused by the formation of strong intermolecular hydrogen bonds, whereas in water zwitterionic structures with the protonation of both nitrogen atoms are formed.     

From 1,2,4-triazines towards substituted pyridines and their cyclometallated Pt complexes

A new, efficient methodology for the synthesis of substituted thienylpyridines includes the synthesis of 3-thienyl-1,2,4-triazines using simple heterocyclisation followed by easy transformation of the triazine ring to a pyridine through an aza Diels-Alder approach. A variety of substituted pyridines can be easily achieved using cheap, commercially available reagents such as bromoacetylarenes, aroyl hydrazides, norbornadiene, and enamines in various combinations. New thienylpyridines form phosphorescent cyclometallated Pt complexes.     

Anodic stripping determination of Pt(IV) based on the anodic oxidation of In from electrochemically deposited Pt–In alloy phases

A simple, rapid, and sensitive anodic stripping voltammetric method for the determination of Pt (IV) is described. It is based on depositing an intermetallic indium–platinum alloy phase on the surface of a modified graphite electrode, and recording the oxidation peak of indium from that alloy phase with the help of linear scan voltammetry. A systematic study of the behavior of different In–Pt phases revealed that the peak potential of indium oxidation from the different phases can be explained on the basis of simple thermodynamic considerations. Different alloy phases have characteristic peak potentials. For the purpose of analysis, it is possible to choose such conditions that only one specific alloy phase forms, viz. PtIn. This is the case for a concentration (milligrams per liter) ratio of In(III)/Pt(IV)?=?50,000:1, at least.     

Spallation reactions in shock waves at supernova explosions and related problems

The isotopic anomalies of some extinct radionuclides testify to the outburst of a nearby supernova just before the collapse of the protosolar nebula, and to the fact that the supernova was Sn Ia, i.e. the carbon-detonation supernova. A key role of spallation reactions in the formation of isotopic anomalies in the primordial matter of the Solar System is revealed. It is conditioned by the diffusive acceleration of particles in the explosive shock waves, which leads to the amplification of rigidity of the energy spectrum of particles and its enrichment with heavier ions. The quantitative calculations of such isotopic anomalies of many elements are presented. It is well-grounded that the anomalous Xe-HL in meteoritic nanodiamonds was formed simultaneously with nanodiamonds themselves during the shock wave propagation at the Sn Ia explosion. The possible effects of shock wave fractionation of noble gases in the atmosphere of planets are considered. The origin of light elements Li, Be and B in spallation reactions, predicted by Fowler in the middle of the last century, is argued. All the investigated isotopic anomalies give the evidence for the extremely high magneto- hydrodynamics (MHD) conditions at the initial stage of free expansion of the explosive shock wave from Sn Ia, which can be essential in solution of the problem of origin of cosmic rays. The specific iron-enriched matter of Sn Ia and its MHD-separation in turbulent processes must be taking into account in the models of origin of the Solar System.     

Properties of destructively modified flocculants

The destructive modification of Magnaflok-919 high-anion polyacrylamide under the action of a microwave irradiation was studied. As a result a new, more effective flocculant was obtained, which allows valuable alimentary components (protein and edible fat) to be completely extracted from milk industry sewage.     

Competitive Formation of β-Amino Acids,Propenoic, and Ylidenemalonic Acids by the Rodionov Reaction from Malonic Acid,Aldehydes, and Ammonium Acetate in Alcoholic Medium

The Rodionov reaction of 49 available aliphatic and aromatic aldehydes with malonic acid and ammonium acetate in alcoholic medium, resulting in formation of β-amino acids, propenoic, and ylidenemalonic acids, was studied. Certain regioselectivity regularities of the reaction were revealed. Among the variety of ketones studied, cyclohexanone is the only whose reaction yields a β-amino acid. Unusual dehydrofluorination of 6-chloro-2-fluorocinnamic acid under the Rodionov reaction was discovered.__________Translated from Zhurnal Obshchei Khimii, Vol. 75, No. 7, 2005, pp. 1177–1186.Original Russian Text Copyright © 2005 by Lebedev, Lebedeva, Sheludyakov, Kovaleva, Ustinova, Kozhevnikov.     

Organosilicon synthesis of isocyanates: II. Synthesis of aliphatic, carbocyclic, and fatty-aromatic isocyanates

Silylation of a series of aliphatic, carbocyclic, and fatty-aromatic amines gave the corresponding silyl derivatives whose yield depended on the electronic and steric structure of the substrate and the nature of the silylating agent. The yield of isocyanates obtained by phosgenation of the silyl derivatives under mild conditions decreased in going from aliphatic amines to benzylamines and rose as the length of the alkyl chain in fatty-aromatic amines extended. The most convenient procedure for the synthesis of low-boiling alkyl isocyanates was found to be based on the transformation of amines or ammonium salts into silyl or silyl silyl-carabamates, followed by pyrolysis of the latter in the presence of trichloro(phenyl)silane.     

Synthesis and N-Alkylation of 2-Alkyl-and 2-Arylimidazole-4,5-dicarboxylic acid esters

Nitration of d-tartaric acid, followed by treatment of the resulting dinitrotartaric acid with ammonia and aldehydes gave 2-phenyl-, 2-(2-pyridyl)-, 2-isopropyl-, and 2-isobutylimidazole-4,5-dicarboxylic acids. Some factors affecting the yield of the final products were revealed, and optimal conditions for their esterification were found. N-Alkylation of 2-substituted imidazole-4,5-dicarboxylates thus obtained involves considerable steric hindrances; therefore, the corresponding N-alkyl derivatives can be obtained in a poor yield only in the presence of such a strong base as 1,8-diazabicyclo[5.4.0]undec-7-ene. Original Russian Text A.V. Lebedev, A.B. Lebedeva, V.D. Sheludyakov, E.A. Kovaleva, O.L. Ustinova, V.V. Shatunov, 2007, published in Zhurnal Obshchei Khimii, 2007, Vol. 77, No. 5, pp. 855–859.